Starting Build of UV/LCD Resin 3D Printer
Starting Build of UV/LCD Resin 3D Printer
Over the last few years, I’ve been assembling 3d printers, modding 3d printers, and then started designing and building my own 3d printers from scratch. These have all been FDM(Filament Deposition Modeling) printers.
This build is my first resin printer. I had originally considered buying one from FormLabs or Monoprice, but thought it would be more fun to build my own from scratch.
Common Design Traits of Liquid Resin Printers
So design does not happen in a vacuum. I’ve looked at the designs of the various resin printers out there, and mechanically, they are significantly simpler than any FDM printer, in that there are quite a few less electro-mechanical moving parts, consisting mainly of a single axis of motion in the form of a screw drive Z-axis driven by a stepper motor.
The X and Y axis are jointly handled by one of the following methods:
- Single point laser drawing the regions of the sliced layer.
- Intense light(visible or UV) displaying the cross-sectional slice via a projector(DLP/Digital Light Projector).
- Single point or array light source masked by an LCD panel with the back light removed.
The build plate is usually a flat aluminum plate with the build surface facing downward. The downward facing surface is where the cured resin will adhere to.
The container holding the resin, commonly referred to as the “vat”, is most often made with aluminum, acrylic, or some other non-reactive material for the sides. The bottom would be made from a thin film comprised of FEP, a non-stick Teflon® material. A variation of this design is one employed by Carbon, which uses an oxygen permeable membrane to introduce oxygen to the UV curable resin, which inhibits curing. This allows for a continuous printing process vs the layer-by-layer process of most printers.
Underneath the vat would be a thin transparent cover glass, then the relevant development system.
The development/printing process works as follows for a UV/LCD printer:
- Original 3D model/object is sliced using a slicer into a series of cross sectional slices along the Z axis. Supports might be added manually or by the slicer to ensure the object is printed properly.
- The printer lowers the build plate into the vat of resin, pressing against the bottom of the vat.
- The pattern is displayed on the LCD panel.
- The UV curing light source is turned on and left on for a period of time, before being shut down.
- The build plate is raised slightly to separate the plate from the vat, some time is allowed for resin to flow in, then the plate is lowered back down, but 1 additional layer height higher than before.
- Rinse and repeat: display pattern, light source on, light source off, raise, lower.
- In this manner, an object slowly emerges from the vat of resin.
- Once the object is fully printed, the build platform is raised further up and stops there, allowing the print to slowly drip off any excess resin until someone comes by to remove the print from the printer.
- The print is cleaned using either isopropyl alcohol or methylated spirits, to dissolve the excess uncured resin off of the printed object, then the object is further cured in a light chamber.
Other steps involve removing supports, either before or after curing. But for the most part, this is the overview of the operation of a liquid resin 3d printer.
So the core idea of a liquid resin 3D printer is pretty straight forward, mechanically.
Sketching Out Ideas
To sketch out the ideas, I originally used pen and paper…. the actual physical items, not an app. 🙂 However, to get a better sense of dimensions and spacing, I turned to OpenSCAD to realistically model the parts and placement. I went through a few iterations, starting with figuring out how the z axis slide carriage would look like.
For my FDM printer builds, I have always used round hardened linear rods of the 8mm variety along with the appropriate linear bearings. They are very inexpensive and increasing dimensions just required extending of the rods.
However, these rods did not constrain rotation and also had a bit of flex to them. So instead, I looked at linear rails with MGN12 carriages, which are MUCH stiffer, better constrained, and provide screw threw mount points for ensuring rigid reinforcement as well as stability.
For the frame of the printer, my goal was to ensure rigidity as well as provide a good deal of mount point options. Aluminum extrusions were a natural choice for this. However, instead of using 10mm or 15mm aluminum extrusions, I went with 20mm profile extrusions in the 40x40mm configuration for the vertical column and 20x80mm for the four sides of the frame. For the brackets, instead of 3D printing brackets, which have all eventually failed or allowed for flexibility, in the past, I opted to go with standard metal right angle brackets that took 4 bolts for each side.
Initial Assembly of Frame Components
To better understand my sketches, I bought some cut to length aluminum extrusions and mounting brackets from Misumi USA and started assembling the frame components to get a sense of how things will look.
Updating Design Based On Feedback
I posted some initial sketches on Facebook and got some feedback, leading me to consider making changes to my design. The core change is that I moved away from the cantilever bed design, and went with a dual Z-axis threaded setup.
My design will use a 10.1″ diagonal LCD panel, which potentially can generate a great deal of force during the lift and during the push, which would risk tilting a single column, but with two columns with both the common arm and a top brace.